A binary operation ? ? is defined is defined by a ? ? b = a + b + 1 for any real numbers a and b. Find the inverse of the real number 7 under the operation ...

A binary operation $?$ is defined is defined by a $?$ b = a + b + 1 for any real numbers a and b. Find the inverse of the real number 7 under the operation $?$, if the identify element is -1

Answer Details

a $\Delta$ b = a + b + 1
a $\Delta$ a-1 = e
7 $\Delta$ 7-1 = 7 + 7-1
therefore 7-1 = -1 - 8
= -9
the inverse of 7 under the operation $\Delta$ is -9